Of the trace metals, zinc is the second most abundant metal in the human body, catalyzing nearly every bio-process directly or indirectly through inclusion in many different metalloenzymes. The critical role zinc plays can be discerned from the symptoms of dietary deficiency, which include dermatitis, anorexia, alopecia and impaired overall growth. Zinc appears especially important to skin health and has been used (typically in the form of zinc oxide or calamine) for over 3000 years to control a variety of skin problems. Recent data more specifically points to the healing and repairing properties of topical zinc treatment to damaged skin, often resulting in increased rates of healing. There is a growing body of biochemical support for this phenomenon. Since dandruff has been previously shown to represent significant damage to scalp skin, topical zinc treatment could aid in the repair process.
Inorganic salts, such as zinc hydroxycarbonate and zinc oxide, have been employed as bacteriostatic and/or fungistatic compounds in a large variety of products including paints, coatings and antiseptics. However, zinc salts do not possess as high of a level of biocidal efficacy as might be desired for many anti-dandruff and skin care applications.
Despite the options available, consumers still desire a shampoo that provides superior anti-dandruff efficacy along with improved conditioning benefit for dry hair, while not interfering with the cleansing or anti-dandruff efficacy, nor providing negative feel to the hair when it is dried. Such a combination can be difficult.
Shampooing cleans the hair by removing excess soil and sebum. However, shampooing can leave the hair in a wet, tangled, and generally unmanageable state. Once the hair dries, it is often left in a dry, rough, lusterless, or frizzy condition due to removal of the hair's natural oils and other natural conditioning and moisturizing components. The hair can further be left with increased levels of static upon drying, which can interfere with combing and result in a condition commonly referred to as “fly-away hair.”
A variety of approaches have been developed to alleviate these after-shampoo problems. These approaches range from post-shampoo application of hair conditioners such as leave-on and rinse-off products, to hair conditioning shampoos which attempt to both cleanse and condition the hair from a single product.
In order to provide hair conditioning benefits in a cleansing shampoo base, a wide variety of conditioning actives have been proposed. However, many of these actives have the disadvantage of leaving the hair feeling soiled or coated and of interfering with the cleansing efficacy of the shampoo.
Coacervate formation in a shampoo composition is known to be advantageous for providing conditioning benefits to the hair. The use of cationic polymers to form coacervate is known in the art, such as in PCT publications WO 93/08787 and WO 95/01152. However, these shampoo compositions are good for delivering wet hair conditioning but are not capable of delivering satisfactory dry hair clean/smooth feel.
Based on the foregoing, there is a need for a conditioning shampoo which can provide improved conditioning benefit for dry hair, while not interfering with the cleansing efficacy, nor providing negative feel to the hair when it is dried. Specifically, there is a need for a shampoo which provides superior anti-dandruff efficacy and further provides long lasting moisturized feel, clean/smooth feel, and manageability control to the hair when the hair is dried, yet not leave the hair feeling greasy, as well as to provide softness and ease of combing when the hair is wet.
None of the existing art provides all of the advantages and benefits of the present invention.